Morphology and kinematics in clusters of galaxies

The existence of subclustering, infall, and the morphology-local density relation suggests that there should be differences in the kinematics of different morphological populations in clusters. From published data, we compile a sample of galaxy redshifts and types in six rich clusters of galaxies: A548, A1060, A1644, A1656, A2151, and DC 2048-52. In three clusters, the velocity distribution of spiral galaxies is different from those of other morphological populations: (1) spirals and ellipticals differ in A1656 and A2151, and (2) spirals and SO's differ in DC 2048-52. The differences in the distributions result primarily from differences in the mean velocities. The results are consistent with a picture in which a cluster irregularly accretes clumps of mostly spiral galaxies from the field, causing the combined velocity distribution to be asymmetric. These clumps might infall within the plane of a wall like the Great Wall of galaxies [Geller & Huchra, Science, 246, 897 (1989)]. Recent dynamical simulations show that the asymmetries may persist until after the clumps have merged with the central mass concentration [van Haarlem, PhD. thesis, Leiden University (1992)].